S22 - Session O1 - Large scale cultivation of dye plants: the example of madder (Rubia tinctorum L.) and weld (Reseda luteola L.)

Authors: Florent Glatard *, Anne de la Sayette

Requests from consumers for natural and environmentally friendly products as well as archaeology research and artwork restoration, allowed natural dyes to do their comeback. However, this revival asks many questions, particularly for their production at industrial scale. ARRDHOR n CRITT Horticole (Rochefort, France) has answered this question for eight dye plants, among them madder and weld. Madder roots contain a large proportion of dyeing molecules like alizarin and other anthraquinone derivatives and aerial part of Weld contain luteolin, a dyeing molecule belonging to the flavonoid family. The objective of our work was to develop a process to cultivate these plants at an industrial level. We first selected during 6 years of cultivation, the best varieties among more than twenty geographical origins. This selection was based on yield of biomass, adaptation to our soils and oceanic climate, yield of extraction and quality of the color. We tested and compared the main crop factors: crop establishments, type of soil, fertilization, irrigation, crop durations, harvesting and post harvesting process. We also tested and adapted the farm machineries to large scale production and particularly those used to harvest madder roots. This work leads to development of cultural practices, follow by the farmers partners of Couleur de Plantes® (Rochefort, France). This allows them to obtain an average yield of 2T of dry matter per hectare, which contain a very good amount of dye with a good colorimetric intensity. The aim is to extend the production from 2 Ha to 10 Ha for each plants a year.